Add Gson converter to MVC config

Issue: SPR-9488

Author: rstoyanchev

spring-webmvc/src/main/java/org/springframework/web/servlet/config/AnnotationDrivenBeanDefinitionParser.java

@@ -20,6 +20,7 @@
 import java.util.Properties;
 
 import org.springframework.web.servlet.mvc.method.annotation.JsonViewResponseBodyInterceptor;
+import org.springframework.http.converter.json.GsonHttpMessageConverter;
 import org.w3c.dom.Element;
 
 import org.springframework.beans.factory.FactoryBean;
@@ -144,6 +145,9 @@ class AnnotationDrivenBeanDefinitionParser implements BeanDefinitionParser {
 			ClassUtils.isPresent("com.fasterxml.jackson.databind.ObjectMapper", AnnotationDrivenBeanDefinitionParser.class.getClassLoader()) &&
 					ClassUtils.isPresent("com.fasterxml.jackson.core.JsonGenerator", AnnotationDrivenBeanDefinitionParser.class.getClassLoader());
 
+	private static final boolean gsonPresent =
+			ClassUtils.isPresent("com.google.gson.Gson", AnnotationDrivenBeanDefinitionParser.class.getClassLoader());
+
 
 	@Override
 	public BeanDefinition parse(Element element, ParserContext parserContext) {
@@ -379,7 +383,7 @@ private Properties getDefaultMediaTypes() {
 		if (jaxb2Present) {
 			props.put("xml", MediaType.APPLICATION_XML_VALUE);
 		}
-		if (jackson2Present) {
+		if (jackson2Present || gsonPresent) {
 			props.put("json", MediaType.APPLICATION_JSON_VALUE);
 		}
 		return props;
@@ -493,6 +497,9 @@ private ManagedList<?> getMessageConverters(Element element, Object source, Pars
 			if (jackson2Present) {
 				messageConverters.add(createConverterDefinition(MappingJackson2HttpMessageConverter.class, source));
 			}
+			else if (gsonPresent) {
+				messageConverters.add(createConverterDefinition(GsonHttpMessageConverter.class, source));
+			}
 		}
 		return messageConverters;
 	}

spring-webmvc/src/main/java/org/springframework/web/servlet/config/annotation/WebMvcConfigurationSupport.java

@@ -44,6 +44,7 @@
 import org.springframework.http.converter.StringHttpMessageConverter;
 import org.springframework.http.converter.feed.AtomFeedHttpMessageConverter;
 import org.springframework.http.converter.feed.RssChannelHttpMessageConverter;
+import org.springframework.http.converter.json.GsonHttpMessageConverter;
 import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
 import org.springframework.http.converter.support.AllEncompassingFormHttpMessageConverter;
 import org.springframework.http.converter.xml.Jaxb2RootElementHttpMessageConverter;
@@ -159,6 +160,9 @@ public class WebMvcConfigurationSupport implements ApplicationContextAware, Serv
 			ClassUtils.isPresent("com.fasterxml.jackson.databind.ObjectMapper", WebMvcConfigurationSupport.class.getClassLoader()) &&
 					ClassUtils.isPresent("com.fasterxml.jackson.core.JsonGenerator", WebMvcConfigurationSupport.class.getClassLoader());
 
+	private static final boolean gsonPresent =
+			ClassUtils.isPresent("com.google.gson.Gson", WebMvcConfigurationSupport.class.getClassLoader());
+
 
 	private ServletContext servletContext;
 
@@ -290,7 +294,7 @@ protected Map<String, MediaType> getDefaultMediaTypes() {
 		if (jaxb2Present) {
 			map.put("xml", MediaType.APPLICATION_XML);
 		}
-		if (jackson2Present) {
+		if (jackson2Present || gsonPresent) {
 			map.put("json", MediaType.APPLICATION_JSON);
 		}
 		return map;
@@ -605,6 +609,9 @@ protected final void addDefaultHttpMessageConverters(List<HttpMessageConverter<?
 		if (jackson2Present) {
 			messageConverters.add(new MappingJackson2HttpMessageConverter());
 		}
+		else if (gsonPresent) {
+			messageConverters.add(new GsonHttpMessageConverter());
+		}
 	}
 
 	/**